Chronic Fatigue Virus?

New evidence suggests (again) that chronic fatigue syndrome may be linked to a virus - but is it cause or effect?

A new study finds that many chronic fatigue syndrome (CFS) sufferers show evidence of a virus known as MLV-related virus lurking in their bodies. Though this might sound familiar, the new study actually reaffirms the virus-CFS link, which had been called into question after several recent studies had been unable to confirm such a connection.

They found that 32 out of 37 - or 86% - of the samples had evidence of the murine leukemia or MLV virus. Only three of the 44 blood samples from healthy controls showed this virus.

Chronic fatigue syndrome is characterized by extreme fatigue, particularly after exercise or mental exertion; muscle weakness; joint pain; sore throat; swollen lymph nodes; insomnia; and cognitive problems. The syndrome has presented somewhat of a mystery to the medical community (not to mention extreme frustration to CFS patients), since the underlying cause has been so unclear.

The researchers of the current study, published in Proceedings of the National Academy of Sciences (PNAS), analyzed CFS patients’ blood samples from 15 years ago. They found that 32 out of 37 - or 86% - of the samples had evidence of the murine leukemia or MLV virus. Only three of the 44 blood samples from healthy controls showed this virus. The authors also looked at some current blood samples from CFS patients and found evidence of the MLV-related virus in seven out of the eight samples analyzed.

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The study is important in that it supports the idea that CFS may be linked to an MLV-related virus. This idea had been questioned after four follow-up studies were unable to replicate the findings in the Science study mentioned earlier, which suggested a strong link between CFS and xenotropic murine leukemia virus-related virus, or XMRV. Still, the authors do caution that it’s too early to make assumptions about causality - that is, whether the MLV-related virus actually causes CFS symptoms or whether there’s something else at play here. It could be, for example, that people who already have CFS are more susceptible to the virus because of "an underlying CFS-related immune dysfunction". It will be interesting to learn the next piece of the CFS puzzle as it’s uncovered.

The study, led by Shyh-Ching Lo, was executed by researchers at Harvard’s Brigham and Women’s Hospital, the FDA, and NIH.